首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   1249篇
  免费   91篇
  国内免费   8篇
耳鼻咽喉   8篇
儿科学   85篇
妇产科学   21篇
基础医学   144篇
口腔科学   15篇
临床医学   129篇
内科学   280篇
皮肤病学   44篇
神经病学   46篇
特种医学   185篇
外科学   109篇
综合类   32篇
预防医学   86篇
眼科学   8篇
药学   58篇
肿瘤学   98篇
  2023年   2篇
  2022年   5篇
  2021年   13篇
  2020年   9篇
  2019年   22篇
  2018年   23篇
  2017年   24篇
  2016年   21篇
  2015年   39篇
  2014年   44篇
  2013年   58篇
  2012年   63篇
  2011年   60篇
  2010年   54篇
  2009年   45篇
  2008年   65篇
  2007年   68篇
  2006年   45篇
  2005年   45篇
  2004年   36篇
  2003年   43篇
  2002年   22篇
  2001年   29篇
  2000年   21篇
  1999年   31篇
  1998年   36篇
  1997年   42篇
  1996年   38篇
  1995年   37篇
  1994年   36篇
  1993年   24篇
  1992年   16篇
  1991年   17篇
  1990年   16篇
  1989年   21篇
  1988年   24篇
  1987年   21篇
  1986年   23篇
  1985年   20篇
  1984年   13篇
  1983年   16篇
  1982年   5篇
  1981年   10篇
  1980年   8篇
  1979年   5篇
  1978年   5篇
  1977年   8篇
  1976年   11篇
  1975年   6篇
  1972年   1篇
排序方式: 共有1348条查询结果,搜索用时 62 毫秒
21.
We analyze different aspects of our quantum modeling approach of human concepts and, more specifically, focus on the quantum effects of contextuality, interference, entanglement, and emergence, illustrating how each of them makes its appearance in specific situations of the dynamics of human concepts and their combinations. We point out the relation of our approach, which is based on an ontology of a concept as an entity in a state changing under influence of a context, with the main traditional concept theories, that is, prototype theory, exemplar theory, and theory theory. We ponder about the question why quantum theory performs so well in its modeling of human concepts, and we shed light on this question by analyzing the role of complex amplitudes, showing how they allow to describe interference in the statistics of measurement outcomes, while in the traditional theories statistics of outcomes originates in classical probability weights, without the possibility of interference. The relevance of complex numbers, the appearance of entanglement, and the role of Fock space in explaining contextual emergence, all as unique features of the quantum modeling, are explicitly revealed in this article by analyzing human concepts and their dynamics.  相似文献   
22.
The present report describes a case of severe airway obstruction caused by endobronchial tuberculosis in an 11-year-old girl who was successfully treated by bronchoscopic balloon dilation. This case illustrates the insidious presentation and the increasingly important role of bronchoscopic intervention in the management of endobronchial tuberculosis. In addition, a brief literature review of the condition in the pediatric age group is included.  相似文献   
23.
Endogenous protein phosphorylation by resting and activated human neutrophils   总被引:10,自引:0,他引:10  
Andrews  PC; Babior  BM 《Blood》1983,61(2):333-340
NADPH oxidase is an enzyme in the plasma membrane of the neutrophil that catalyzes the production of O2-, a species central to the oxygen- dependent killing mechanisms of this cell. The oxidase is dormant in resting cells and is activated upon the addition of a stimulus. Neutrophils of patients with chronic granulomatous disease (CGD) manifest no oxidase activity when stimulated. The possible role of protein phosphorylation in the activation of NADPH oxidase was examined in normal and CGD neutrophils by measuring the incorporation of 32Pi into proteins as determined by gel electrophoresis followed by autoradiography. Resting neutrophils from normal subjects exhibit at least 40 distinct phosphoprotein bands. The level of phosphorylation of these bands was examined after the addition of phorbol myristate acetate (PMA), opsonized zymosan, digitonin, N-formyl-methionyl- phenylalanine (FMLP), or NaF. PMA and opsonized zymosan increased the phosphorylation of a set of 6 protein bands. Digitonin and FMLP consistently caused the phosphorylation of 4 of these protein bands, while NaF failed to induce increased phosphorylation of any protein band. All activators tested caused the dephosphorylation of one specific protein band. The time course of phosphorylation (dephosphorylation) was examined using PMA as the activating agent. Increased phosphorylation of one protein band was evident by 12 sec after the addition of PMA. The most slowly phosphorylated protein band did not slow evidence of change until 5 min after the addition of PMA. Three of the phosphoproteins examined were phosphorylated either earlier than or concomitant with the activation of NADPH oxidase. CGD neutrophils were compared with normal cells for their ability to phosphorylate proteins in response to PMA. The phosphoprotein banding patterns of CGD neutrophils were identical with those of normal neutrophils in both the resting and activated states. The evidence presented shows that the phosphorylation of proteins is a prominent feature of neutrophil metabolism. The striking similarity of phosphorylation changes induced by the various activators tested suggests that protein phosphorylation may play a role in some aspects of neutrophil activation. Evidence was not obtained, however, regarding a link between protein phosphorylation and activation of NADPH oxidase.  相似文献   
24.
Kaplan  AP; Gruber  B; Harpel  PC 《Blood》1985,66(3):636-641
An enzyme-linked immunosorbent assay has been developed for the quantitation of activated Hageman factor-C1 inactivator (HF-C1 INH) complexes. Addition of increasing quantities of either of the major forms of activated Hageman factor (HFa or HFf) to normal plasma or to Hageman factor-deficient plasma leads to a dose-dependent increase in activated HF-C1 INH complexes. As little as 0.5 micrograms/mL of activated HF added to plasma can be detected, corresponding to activation of approximately 2% of plasma HF. The sensitivity of the assay is increased at least tenfold when complexes are formed in HF- deficient plasma, indicating competition between unactivated HF and activated HF-C1 INH complexes for binding to the antibody. Specificity is demonstrated in that addition of activated HF to hereditary angioedema plasma yields less than 1% of the activated HF-C1 INH complex formation obtained with normal plasma. Kaolin activation of HF- deficient plasma yields no detectable complex formation. Kaolin activation of prekallikrein-deficient plasma demonstrates a time- dependent increase in formation of activated HF-C1 INH complex consistent with the ability of HF in this plasma to autoactivate as the time of incubation with the surface is increased. Kaolin treatment of high-molecular weight (HMW) kininogen-deficient plasma yields an even more profound abnormality in the rate of formation of activated HF-C1 INH complexes reflecting the complex role of HMW kininogen in the initiation of contact activation. Although addition of corn inhibitor to plasma prevents activated HF-C1 INH complex formation, it does not inhibit activated HF sufficiently fast to prevent prekallikrein activation.  相似文献   
25.
Amrein  PC; Stossel  TP 《Blood》1980,56(3):442-447
Proteases can complicate the characterization of proteins from cells, especially human polymorphonuclear leukocytes (PMN), which contain abundant neutral proteases. We tested the ability of agents to inhibit proteolysis, with special reference to the subunit polypeptides of the contractile proteins actin, myosin, and actin-binding protein (ABP). Phenylmethylsulfonyl fluoride (PMSF), O-phenanthroline, EGTA, EDTA, N- ethylmaleimide, alone or in combinations, failed to prevent extensive proteolysis of the PMN proteins during solubilization of cells with dodecyl sulfate. These inhibitors and also alpha-1-antitrypsin and soybean trypsin inhibitor similarly could not prevent proteolysis during homogenization of cells in cold isosomolar sucrose. Treatment of PMN with greater than or equal to mM diisopropylfluorophosphate (DFP) prior to solubilization or homogenization markedly inhibited proteolysis. PMSF and DFP were equally effective in inhibiting proteolysis in PMN extracts, suggesting that the efficacy of DFP may result from its permeation of intact cells and granules before barriers are disrupted by detergents or homogenization. Treatment of PMN with DFP under conditions inhibiting proteolysis did not affect their rate of phagocytosis. We recommend the use of DFP in future studies correlating functions and protein structure of PMN.  相似文献   
26.
Niskanen  E; Gorman  J; Isakson  PC 《Blood》1987,70(6):1784-1789
In this study we detected a factor that stimulates the proliferation of bone marrow-derived hematopoietic precursors in diffusion chambers implanted in mice. This factor, called diffusible colony-stimulating factor (D-CSF), was found in medium conditioned in the presence of spleen and peripheral blood cells from mice with B cell leukemia (BCL1). After the administration of D-CSF, the number of colonies formed in the plasma clot inside the chamber (CFU-DG) was increased, as were the number of hematopoietic precursors (CFU-MIX, CFU-S, CFU-C, and BFU-E) as judged by a subculture of diffusion chamber contents. Depletion of macrophages and T cells from the spleen cell suspension did not decrease the production of D-CSF, thereby indicating that it was derived from B cells. Neoplastic BCL1 cells appear to be the source because D-CSF could not be detected in medium conditioned with normal B cells. BCL1-conditioned medium (CM) did not enhance CFU-MIX, BFU-E, and CFU-C colony formation in vitro, which suggested that D-CSF is different from multi-CSF, EPA, or CSF. The addition of BCL1 CM to multi- CSF-, erythroid potentiating activity (EPA), and CSF (EL-4CM)- containing cultures had no effect on CFU-MIX, BFU-E, and CFU-C colony formation, thus indicating the absence of a synergistic or inhibitory activity. On the other hand, EL-4 CM, which stimulates CFU-MIX, BFU-E, and CFU-C in vitro, had no effect on CFU-DG in vivo. Biochemical characterization of BCL1 CM revealed that D-CSF is relatively heat stable and loses its bioactivity with protease treatments. It binds to lentil-lectin, according to gel-filtration chromatography has a relative molecular weight of approximately 43,000, and on reverse-phase high-performance liquid chromatography elutes with acetonitrile. These data also indicate that transformed B cells may serve as a source for hematopoietic regulators that act on hematopoietic precursors in vivo.  相似文献   
27.

Objective

To collect, compile and evaluate publicly available national health accounts (NHA) reports produced worldwide between 1996 and 2010.

Methods

We downloaded country-generated NHA reports from the World Health Organization global health expenditure database and the Organisation for Economic Co-operation and Development (OECD) StatExtract website. We also obtained reports from Abt Associates, through contacts in individual countries and through an online search. We compiled data in the four main types used in these reports: (i) financing source; (ii) financing agent; (iii) health function; and (iv) health provider. We combined and adjusted data to conform with OECD’s first edition of A system of health accounts manual, (2000).

Findings

We identified 872 NHA reports from 117 countries containing a total of 2936 matrices for the four data types. Most countries did not provide complete health expenditure data: only 252 of the 872 reports contained data in all four types. Thirty-eight countries reported an average not-specified-by-kind value greater than 20% for all data types and years. Some countries reported substantial year-on-year changes in both the level and composition of health expenditure that were probably produced by data-generation processes. All study data are publicly available at http://vizhub.healthdata.org/nha/.

Conclusion

Data from NHA reports on health expenditure are often incomplete and, in some cases, of questionable quality. Better data would help finance ministries allocate resources to health systems, assist health ministries in allocating capital within the health sector and enable researchers to make accurate comparisons between health systems.  相似文献   
28.
29.
30.
Summary  We report three siblings with Gaucher disease type III, born between 1992 and 2004. During this period, new developments resulted in different potential therapies, changing clinical practice. The two eldest siblings received enzyme replacement therapy (ERT) from the age of 24 and 5 months respectively, later followed by an increase in dosage. ERT was combined with substrate reduction therapy (SRT) from the ages of 12 and 8 years, respectively. In the youngest sibling the combination of high-dose ERT and SRT was given from the age of 5 months. The two eldest siblings showed significant neurological impairment from the age of 1.5 years, starting with a convergent strabismus and partial oculomotor apraxia, followed by cognitive decline and an abnormal EEG and BAER. In contrast, the neurological development in the youngest sibling is almost completely normal. At the age of 3 years, cognitive development, EEG and BAER are all normal. Disturbed saccadic eye movements, which were already present at the start of therapy, remained stable. In addition to the clinical efficacy, we report on the biochemical response to therapy. Based on our results, the combination of high-dose ERT and SRT should be considered as a possible therapeutic approach for GD III, especially if started at a young age. Further follow-up studies are necessary to explore the long-term therapeutic effects. Competing interests: F.A. Wijburg provides consultancy services for Genzyme Corporation. References to electronic databases: Glucocerebrosidase, EC 3.2.1.45. Gaucher disease type I, OMIM #230800. Gaucher disease type II, OMIM #230900. Gaucher disease type III, OMIM #231000.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号